i’d like you to learn about functionality of internet…
en.wikipedia.org/wiki/SGSN#SGSN_-_Serving_GPRS_Support_Node
SGSN – Serving GPRS Support Node
A Serving GPRS Support Node (SGSN) is responsible for the delivery of data packets from and to the mobile stations within its geographical service area. Its tasks include packet routing and transfer, mobility management (attach/detach and location management), logical link management, and authentication and charging functions. The location register of the SGSN stores location information (e.g., current cell, current VLR) and user profiles (e.g., IMSI, address(es) used in the packet data network) of all GPRS users registered with this SGSN.